Adsorção de eteramina em biomassa de candeia e reutilização em compósito cimentício

Abstract

Iron ore tailings (IOTs) are an environmental problem and are potential sources of recycling of etheramine and sludge. These materials can be inputs for civil construction, thus contributing to sustainable development. Ehteramine is a toxic reagent used in cationic reverse flotation of iron ore that can be treated by means of adsorption, an easy operation technique that can be inexpensive, depending on the adsorbent material. Candeia is a forest specie that generates a by-product in the extraction of its oil: a lignocellulosic material, which was proposed to be used as an adsorbent, also as filling of cementitious composite. For the adsorption of etheramine from aqueous solution, was used natural biomass of candeia, heat-treated biomass of candeia and cooked biomass of candeia. Natural biomass of candeia adsorbed with etheramine was also used as filling in cement composite, along with mud from IOTs as filler. Biomass was characterized by spectroscopy in the infrared region by Fourier transform (FTIR), extractive content, lignin, holocellulose, zeta potential and scanning electron microscopy (SEM). Characteristically functional groups of lignocellulosic materials are present and the surface charge is negative throughout the studied pH range. In the adsorption, experimental optimization of the initial concentration of etheramine, adsorbent mass and pH was carried out through the full factorial design and Central Composite Design (CCD). Through the desirability equation and the response surface methodology, the optimum point of adsorption operation was obtained. The pH 11,5 was the best for all biomasses. For natural biomass, the optimum point was the concentration of 660 mg/L and 11 mg of adsorbent per mL of solution. For heat-treated biomass was the concentration of 186 mg/L and 2,2 mg/mL. For cooked biomass was the concentration of 326 mg/L and 2,2 mg/mL. Kinetic study was better adjusted for Elovich model for all biomasses. Kinetics occurred more quickly for natural biomass. Intraparticle diffusion model showed that several mechanisms are responsible for adsorption. Sips isotherm model obtained the best fit for all biomasses. The maximum amount of adsorption obtained by Langmuir isotherm for natural biomass was 108 mg, for heat-treated biomass was 370 mg and for cooked biomass was 910 mg. To evaluate the performance of the cementitious composite, mud was characterized by pozzolanicity and, along with biomass, were also characterized by chemical composition, density and granulometry. The mechanical and physical properties of the composite were determined: rupture modulus (MOR), elastic modulus (MOE), proportionality limit (LOP), tenacity, porosity, water absorption and density. The incorporation of mud as filler maintained good performance of all properties, compared to limestone, except for density. Incorporation of biomass particles has brought benefits in porosity, water absorption and maintained good performance in MOR, MOE and tenacity if it was inserted together with mud. Therefore, good interaction between mud, natural biomass of candeia adsorbed with etheramine and cement CPV-ARI was evidenced. It is concluded that the natural biomass of candeia performed well both as an adsorbent either as filling in composite (containing mud as “filler”), and that mud is a good filler. In addition, the treated biomasses of candeia increased the amount of adsorbed etheramine, despite slowing down the adsorption process. Finally, sustainable development among iron ore mining, forestry and civil industries is viable.